Well, it matters for everything. If what you're asking is, "Is it critical to have a high refresh rate - does it give the same advantage as it does for FPS games?" then the answer is no. But you can ask yourself the same thing about the very high resolution, too... not only will a heck of a lot of games not support it, but you don't really need it - 1440p is room enough for more hotbars than most people can fathom.
That's fine, go for the 4k monitor then. Since you're used to 60Hz, it will probably be perfectly fine for you. Personally, since I'm used to the smoothness of 120Hz, playing a game on my 1440p, 60Hz monitor feels jaggy and stilted.
is it safe to overclock a monitor like a SAMSUNG U28D590D 4K UHD Display 28? how many frames do you think I could get above normal 70hz maybe? or is it even safe to OC a monitors refresh
People do it. It's not worth it to me.
You run a risk of seriously damaging a very expensive monitor for very little return - 70Hz vs 60Hz is not going to be noticeable. In addition, if you do manage to overclock up to 100 or 120, it's going to look a lot worse than a native 120Hz panel will.